Wt1 Positive dB4 Neurons in the Hindbrain Are Crucial for Respiration

Abstract

Central pattern generator (CPG) networks coordinate the generation of rhythmic activity such as locomotion and respiration. Their development is driven by various transcription factors, one of which is the Wilms tumor protein (Wt1). It is present in dI6 neurons of the mouse spinal cord, and involved in the coordination of locomotion. Here we report about the presence of Wt1 in neurons of the caudoventral medulla oblongata and their impact on respiration. By employing immunohistofluorescence staining, we were able to characterize these Wt1 positive (+) cells as dB4 neurons. The temporal occurrence of Wt1 suggests a role for this transcription factor in the differentiation of dB4 neurons during embryonic and postnatal development. Conditional knockout of Wt1 in these cells caused an altered population size of V0 neurons already in the developing hindbrain, leading to a decline in the respiration rate in the adults. Thereby, we confirmed and extended the previously proposed similarity between dB4 neurons in the hindbrain and dI6 neurons of the spinal cord, in terms of development and function. Ablation of Wt1+ dB4 neurons resulted in the death of neonates due to the inability to initiate respiration, suggesting a vital role for Wt1+ dB4 neurons in breathing. These results expand the role of Wt1 in the CNS and show that, in addition to its function in differentiation of dI6 neurons, it also contributes to the development of dB4 neurons in the hindbrain that are critically involved in the regulation of respiration.

Every Beat You Take—The Wilms′ Tumor Suppressor WT1 and the Heart

“…Inhibition of the outgrowth of the epicardium abolished the response to adrenaline administration, indicating that the epicardium is necessary for a normal response of the heart to adrenaline during early cardiac development [ 53 ]. This report further confirmed a role of Wt1 in neural function, as suggested by several studies [ 23 , 54 , 55 , 56 , 57 , 58 , 59 ].…”

Axonal Projection Patterns of the Dorsal Interneuron Populations in the Embryonic Hindbrain

“…Derived from Neurog1/2 progenitor domain, dB4 INs are inhibitory and express a combination of markers including Lhx1/5, Pax2, bHLHb5, Wilms tumor protein (Wt1), and presumably also the double sex/male abnormal 3 (DMRT3) (Figures 1B,C) (Gross et al, 2002;Müller et al, 2002;Sieber et al, 2007;Gray, 2008;Pagliardini et al, 2008;Hernandez-Miranda et al, 2017;Schnerwitzki et al, 2020). Notably, their spinal cord homolog group dI6, which shares a similar molecular profile and DV localization as dB4, was found to consist of three distinct subgroups, based on their singular or co-expression of Wt1 and/or DMRT3 (Gross et al, 2002;Helms and Johnson, 2003;Vallstedt and Kullander, 2013;Hernandez-Miranda et al, 2017;Schnerwitzki et al, 2020). dI6 neurons were found to migrate to the ventral horn of the spinal cord and to coordinate locomotion in different mammals (Andersson et al, 2012;Vallstedt and Kullander, 2013;Haque et al, 2018;Schnerwitzki et al, 2018).…”

“…In a previous study, hindbrain WT + neurons were discovered in the AP nucleus, suggesting that dB4/WT + neurons may be fated to contribute an inhibitory module to this nucleus, in addition to the presence of excitatory dA3 neurons in the AP (Sharma et al, 1992). Recent data have uncovered an additional fate of Wt1 + neurons in the caudal ventral respiratory group (cVRG) (Schnerwitzki et al, 2020). This neuronal cluster is positioned in the caudal-most part of the respiratory column and is known to participate in the activation of motor neurons in the cervical spinal cord, which in turn innervate the diaphragm muscles, leading to their contraction and thereby to inspiration (Ezure et al, 2003;Alheid and McCrimmon, 2008).…”

“…This neuronal cluster is positioned in the caudal-most part of the respiratory column and is known to participate in the activation of motor neurons in the cervical spinal cord, which in turn innervate the diaphragm muscles, leading to their contraction and thereby to inspiration (Ezure et al, 2003;Alheid and McCrimmon, 2008). As such, ablation of Wt1 + neurons resulted in the death of neonates due to the inability to initiate respiration, suggesting a vital role for Wt1 + neurons in breathing (Schnerwitzki et al, 2020). Since WT expression in the dINs is restricted to the dB4 subgroup, these results strongly suggest the contribution of the dB4 subgroup to respiratory control.…”

Implications of the Wilms’ Tumor Suppressor Wt1 in Cardiomyocyte Differentiation

“…It is known that Wt1 regulates development and maintenance of various tissues of the cardiovascular, urogenital, nervous, hematopoietic, and immune system [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] through regulation of genes involved in proliferation, differentiation, and apoptosis—the essential processes for establishing early cellular fates within the embryo [ 23 , 24 , 30 , 31 , 32 , 33 , 34 ]. The crucial role of Wt1 in heart formation became clear when it was shown that homozygous deletion of Wt1 in mouse embryos was lethal, due to disturbed cardiac development [ 23 , 33 ].…”